We have studied blast transformation of peripheral blood lymphocytes in insulin independent diabetic patients compared to nondiabetic subjects. We have used Staphylococcus aureus antigen and phytohemagglutinin. We have found a defect in the response to staphylococcal antigen, but not to phytohemagglutinin. We propose to further define this defect by enlarging our groups of diabetics to include juvenile diabetics and noninsulin dependent diabetics, to determine the distribution of this defect among diabetic subjects. In addition, we propose to use other bacterial antigens in this assay to determine whether this is a specific or nonspecific defect. We further plan to study leucocyte migratory inhibition factor and cutaneous delayed hypersensitivity in diabetic and nondiabetic subjects to try to find at what level of the lymphocyte mediated cellular immune response this defect exists.